Reference crystal oscillators are typically tuned using variable capacitors or varactor diodes, however oscillators designed with capacitors or varactors do not provide sufficient frequency variation with small variations in bias voltage. Communications products, such as DECT (Digital European Cordless Telephone) and CT-2 (Cordless Telephone Second Generation), continue to reduce their operating supply voltages in an effort to reduce current drain and reduce the number of battery cells required for operation of portable electronic devices. The varactor diode characteristics over temperature at low bias voltage exhibit larger variation than at high bias voltage causing large changes in oscillator frequency. Large signal amplitudes can forward bias the varactor diode and must be avoided in these circuits. Hence, there is a need for an improved frequency tuning circuit that can operate at low voltages while maintaining good temperature performance over a wide frequency tuning bandwidth.